Sound amplifying system



Nov. 3, 1931.

F. HETZEL 1,829,991

SOUND AMPLIFYING SYSTEM Filed June 3. 1929 2 Sheets-Sheet l Fa. TER

drtom Nov. 3, 1931. F. HETZEL 1,829,991

SOUND AMPLIFYING SYSTEM Filed June 3, 1929 2 Sheets-Sheet 2 z2 I 2h W. J

flwwmtoz WLW Patented Nov. 3, 1931 UNITED STATES PATENT OFFICE FRANKHETZEL, LOS ANGELES, CALIFORNIA, ASSIGNOR T0 C. E. HOOVEN, OF

I HAMILTON, OHIO SOUND AIPLHYING SYSTEM.

Application filed .Tune 3, 1929. Serial No. 368,087.

a small pulsating electric current which has a frequency andcharacteristics corresponding to the frequency and characterist cs ofthe original sound. This small current 1s am: plified, andbelectromagnetic means, controls an air va ve, to control the volume ofair released through a loud speaker. The air valve vibrates at the samerate that the' current varies, and so gives a pulsating air currenthaving the same characteristics as the original sound, only in muchgreater volume.

An important feature of the invention is the electromagnetic unit, whichcomprises a pair of electromagnets, the armatures- Of which areconnected to control the movements j of the air valve. Theelectromagnets are connected inv series or parallel, and operate abridgemember which is connected to the valve. The bridge member isvariably posttionable, and 'it is balanced by resilient dezli-v'iceslightly opposing its movement.

' The above described and other features of the invention will bedescribed by reference to the accompanying drawings, illustrating, moreor, less diagrammatically, the preferred embodiment of the invention. i

In the accompanying drawings:

Fig. 1 shows in diagrammatic view the entire apparatus Fig. 2 shows aswitch.

Fig. 3 is a horizontal valve box.

' Fig. 4 is an endview of the valve box and associated parts; and

Fig. 5 is an enlarged side view, partly in section, of theelectromagnetic unit and valve section through the parts, amicrophone 5,is connected by wires 6 with an amplifier 7; a radio receiving set 8 isalso connected bywires 9 with the amplifier 7; a phonograph 10,.providedwith a transmitter sound. "box 12, connected to a sourceofcurrentbywires 13, and sends a variable current-to the amplifier 7 byWires 14.

The microphone, the radio receiving set and the phonograph each producesa varying electric current, having frequencies and characteristicscorresponding to the frequencies and characteristics of the originalsources of the sound. The three elements just described ma beindividually connected with the ampli er by a three-way switch 11 as inFig. 2.

The amplifier 7 may be of any known or suitable type, containing usuallythree or four vacuum tubes, for amplifying the weak currents produced bythe microphone, radio set or phonograph to suitable strengths foractuating the electromagnets and loud speaker, now to be described.

" The loud speaker 15 is of the type where a current ofair underpressure is supplied thereto, the amount of air released through theloud speaker being controlled by a carefully balanced valve, which movesat a rate and atan amount corresponding to the frequenciesand'characteristics of the original source of sound. The valve iscontrolled by electromagnetic means, which in turn are actuated by theamplified current from the amplifier,7.- 1

The valve for the loud speaker is indicated at 16; it is connected by a.connector 17 to the bridge member 18 of an electromagnetic unitcomprising two substantially U-shaped electromagnets 19 and 20 carriedby the frame 22.

Armature 23 of electromagnet 19 is pivoted at its lower end andconnected, as by pivot pin 24, with the bridge member 18; armature 25 ofelectromagnet 20 is pivoted at its lower end and connected, as by pivotpin 26, with the bridge member 18. The movement of the bridge member 18is opposed in one direction by a resilient element 27, carried byelectromagnet 20 and in the other direction by a resilient element 28,carried by rod 29. These resilient elements act to balance the bridgemember, but do not stop its movement in either direction in response tothe electromagnets.

- The bridge member 18 is manually set-table in desired adjustedposition by a set screw 30, mounted in bracket 32, which bears againstthe rod 29. A lock nut 33 locks the set screw in adjusted position. Thedegree I the valve box is a plate 36 provided with a lurality of slotsforming a grated exit or the air this grated exlt being normally closedby -,the ,flat .valve-plate member -16.

The positioning of the plate 36 is controlled,

by the threaded bolts 38, having manually actuable heads 39. Air, undera pressure of approximately 27 pounds is supplied to thevalvebox from apipe 40, the air being filtered by a mass of fibrous material 42 beforeit reaches thevalve plate 36.

The valve 16 has a fiat-face which normally is against plate 36, toclose the grating 37 the valve is pivotally mounted: The valve hassupporting arms 44, supported by plate i5, carrying pivot points 46 forminimlzing friction. A resilient arm 47 is connected to the valve, theresilience of which is controlled by a set screw 48. I

As the bridge member 18 vibrates rapidly in response to theelectromagnets 19 and 20, the valve 16, pivoting about points 46, opensandcloses correspondingly, thereby controlling the amount of airreleased to the loud speaker 15 by pipe 49, and produces a pulsating aircurrent having the characteristics of the original sound, therebyreproducing the a original sound, amplified as many times as desired.The degree of amplification may adjusted by controlling the amount ofampll fication in 7, as by the usual volume control handle 50, and bycontrolling the amount of airsupplied to the valve box 35 by pipe 40.

This may be controlled by a valve 52 in pipe 40, by controlling thespeed of the air compressor,etc.

' In the device as actually used, there are four units, that is, foursets of electromagnets 19 and 20, four valves 16, four valve boxes 35,etc. all feeding air into one loud speaker 15. By using one or more, orall, of the units, the volume of sound can be controlled over a widerange. In actual practice, the sound from the loud speaker could easilybe heard at a distance of a quarter to half a mile, and greaterdistances under quite conditions.

The valve box 35 may be adjustably supported by a bracket 55, having atubular part 56 which is movable up and down on a threaded support 57,the positioning being controlled by nuts 58.

The described apparatus has been designed for and used on a motor truck.In order to compensate for inequalities in the road, the

phonograph may be pivoted in a ring 60by pivots 61, ring 60 beingpivoted on an axis at right angles, in a bracket 62.

Compressed air from a compressor passes into a tank 66, then through anair filter 67 and throu h balance tanks 68 and 69, the several tankseeping the air pressure more nearly uniform.

' While one embodiment of the invention has been described in somedetail, it should be understood that the invention is not to be limitedto thesedetails, but may be carried out in a loud speaker, means forsupplying air un-" der pressure thereto, a pivotally mounted valve forcontrolling the amount of air released through the loud speaker, a pairof electromagnets, a bridge member actuated b y the electromagnets,means connecting the bridge member and valve, and means for supplying avariable electric current to the electromagnets.

3. A sound amplifying system, comprising a loud speaker, means forsupplying air under pressure thereto, a valve controlling the amountofair released through the loud speaker, a pair of electromagnets, abridge member actuated by the electromagnets, manually settable meansfor varying the movement of the valve with respect to the throw of thebridge member, and means operatively connecting the bridge member andthe valve for operating the valve.

4. A sound amplifying system, comprising a loud speaker, means forsupplying air under ressure thereto, a pivotally mounted valve orcontrollin the amount of air released through the loud speaker, a pairof electromagnets, a bridge member actuated by the electromagnets, meansfor variably positioning the bridge member, and means operativelyconnecting the bridge member and the valve for operating the valve.

5. A sound amplifying system, comprising a loud speaker, means for suplying air under pressure thereto, a pivota y mounted valve forcontrolling the amount of air released through the loud speaker, a pairof electromagnets, a bridge member actuated by the electromagnets, meansfor variably positioning the bridge member, means for supplying a varyincurrent havin the frequencies of soun waves, to the e ectromagnets, andmeans operatively connecting the bridge member and the valve foroperating the valve. 6. A sound amplifying system, comprising a loudspeaker, means for supplying air under pressure thereto, a valve forcontrolling the amount of air released through the loud speaker, a pairof substantially U-shaped electromagnets, an armature for eachelectromagnet, a bridge member connected to both armatures, and alsoconnected to the valve for controlling it, and means for supplying avarying electric current to the electromagnets.

7 A sound amplifying system, comprising a loud speaker, means for suplying air under pressure thereto, a valve or controlling the amount ofair released through the loud speaker, a pair of substantially U-shapedelectromagnets, an armature for each electromagnet, a bridge memberconnected to both armatures, and also connected to the valve forcontrolling it, means for supplying a varying electric current to theelectromagnets, and manually settable means for varying the movement ofthe valve with respect to the throw of the bridge member.

8. A sound amplifying'system, comprising a loud speaker, means forsupplying air under ressure thereto, a pivotally mounted valve orcontrolling the amount of air released through the loudspeaker, a pairof electromagnets, a bridge member actuated thereby and operativelyconnected to said valve, resilient means opposing the throw of thebridge member, and means for supplying a varying electric current to theelectromagnets.

9. A sound amplifying system, comprising a loud speaker, means for suplying air under pressure thereto, a valve or controlling the amount ofair released through the loud speaker, a pair of electroma ets, a bridgemember actuated thereby an operatively connected to said valve,resilient elements opposing the movement of the brid e member in eitherdirection, and manual y settable means for controlling the movement ofthe valve.

10. A sound amplifying system compris- 5 ing in combination a pair ofelectromagnets, each having an armature, a bridge member pivotallyconnected to each armature, a pivotally mounted valve, operativelyconnected to the bridge member, a grated seat for the valve, means firsupplying air under pressure to said grated seat, and means forsupplying a varying electric current to the electromagnets.

In testimony whereof I aflix my si ature. FRANK L. HE EL.

